Rotor for rotor sustained aircraft



May 23, 195o P. J. BRouwER ROTOR FOR KOTOR SUSTAINED IRCRAFT 3 Sheet's-Sheet 1 Filed Jan. l2. 1945 O. vill .5. ,r A MM Zhwentor PIETER J. BROUWER May 23, 1950 P. J. BRouwER l 2,509,128

ROTOR FOR ROTOR SUSTAINED AIRCRAFT Filed Jan. 12, 1945 :3 sheets-sheet 2.

. l Q 22/ I u I8 I9 rwentor PIETER* .1.- BRouwER (Ittorneg May 23, i950 Filed Jan. 1,2, '1945 P. J. BROUWER ROTOR FOR ROTOR SUSTAINED AIRCRAFT 3 Shee'ts-Sheet 5 INVENTOR.

PIETER J. BROUWER ATTORNEY Patented May 23, 195,0

ROTOR FOR ROTOR SUSTAINED AIRCRAFT Pieter J. Brouwer, Los Angeles, Calif., assignor to Gilbert W. Magill, Los Angeles, Calif.

Y Application January 12, 1945, Serial No. 572,505

This invention relates to helicopters, and has as its general object to provide an improved helicopter rotor of the type in which the angle of the blades is adapted to .be changed during operation thereof so as to effect feathering and paddling movements which are utilized in stabilizing and controlling the operation of the helicopter.

One useful application of the invention is in a tandem rotor helicopter of the general type disclosed in the abandoned application of Gilbert W. Magill, Serial No. 565,564, filed October 8, 1943, although the invention may be applied as well to other helicopters such as, for example, a single rotor or a co-axial rotor type helicopter.

The adjustment of -blade angle in a helicopter rotor during flight operation may be utilized for a number of purposes. By controlling the blades in such a manner that the blade which is moving rearwardly with reference to the direction of iiight assumes a position transverse to the general plane of rotation of the rotor while the blade moving forwardly with reference to the lineA of night assumes a position lying more nearly in the rotor plane, the rotor may be caused to paddle the craft forwardly in the air. When a blade on one side of the ship assumes an angle of greater lift than a blade on the other side, a tendency of the ship to roll or tilt around its longitudinal axis may be counteracted. A blade moving laterally on the forward side of the rotor may be caused to paddle while a blade moving laterally in the opposite direction on the rear side of the rotor may be given a feathered position, in order to give the craft a sidewise movement or a component of sidewise movement. It may be desirable to change the angle of all of the blades of the rotor simultaneously so as to vary the effective lift of the rotor. Various combinations of these adjustments may become desirable under varying'conditions of flight.

To achieve either simultaneous or independent adjustment of the blades of a helicopter rotor requires a control mechanism which is closely coordinated with the shaft on which the blades are mounted for rotation. Where provision is to ybe made for the independent control of the several blades of two rotors arranged in tandem, it is desirable to provide means for interlinking the control of one rotor with the control of the other and since a substantial proportion of the rotor shaft will ordinarily project above the fuselage of the helicopter and it is preferable to have the interlinking control mechanism located within the fuselage, it is desirable to bring the con- 9 Claims. l (Cl. 170-160) trol mechanism from the blades down along the rotor shaft and to connect such control mechanism with interlinking control mechanism which bridges across between the lower portions of the rotor shaft. v

In order to reduce aerodynamic drag and to protect the vertically extended control members against damage from the weather and other causes, I propose to employ an arrangement in which these control members are housed within the rotor shaft, which is made tubular for that purpose, as well as to achieve maximum strength coupled with minimum weight.

In order to translate the longitudinal movement of a control member such as a rod extending vertically through the tubular rotor shaft, into oscillatory movement of the rotor blades, the invention contemplates the use of a crank arm on the blade. This involves a problem of avoiding complications which would arise from attempting to connect up the end of such a crank arm (which, with the rotor blade arranged conventionally with its axis intersecting that of the rotor shaft, would project radially outwardly from the rotor shaft) with the control rod coming up through the rotor shaft. One of the objects of the invention is to lprovide a rotor hub of such construction and arrangement as to permit the use of a relatively simple operating linkage in which a crank arm, secured to the shank of a rotor blade, is connected directly to the control rod coming upwardly through the rotor shaft, and in which no intermediate linkage is required.

Another object of the invention is to provide a rotor hub having maximum strength coupled with minimum size, in order to reduce weight and aerodynamic drag to a minimum.

Having in mind the foregoing objects, the invention provides a rotor hub assembly in which the rotor blades are arranged tangentially with the Shanks thereof arranged to define the perimeter of a polygon (an equilateral triangle where there are three blades) with the several crank arms extending inwardly and terminating above the tubular rotor shaft, and with the distance from the axis of rotation to the outermost extremities of the hub being less than the distance between the bearing points where the load of the helicopter is transferred from the hub to the blades.

A further object of the invention is to provide a helicopter rotor, in which the weight of the hub is reduced by balancing the down load on the end of one blade shank against the upload at an intermediate point in an adjacent shank.

A further object is to provide an open hub construction which improves the accessibility to the parts thereof.

Another object of the invention is to provide a helicopter rotor in which the bending moments on the blades in the plane of the rotor are reduced by balancing a component of centrifugal force against a portion of thedrag load on each blade.

Further objects and advantages of they invention will be brought out in the following part of the specification.

Referring to the drawings which are for illustrative purposes only,

Fig. 1 is a plan view, partially in section, of a helicopter rotor hub embodying the invention;

Fig. 2 is a vertical axial sectional view of a portion thereof, taken on the line 2 2 of Fig. 1;

Fig. 3 is a sectional view taken on the line 3 3 of Fig. l;

Fig. 4 is a sectional view taken on the line 4 4 of Fig. 1;

Fig. 5 is a plan view and stress diagram 'of the rotor;

Fig. 6 is a fragmentary plan View, partially in section, of a portion of a rotor embodying a modication ofthe invention; Y

Fig. 1 is'a side elevation, partially in section, of a rotor hub embodying another modification of the invention; and

Fig. 8 is a plan view of a rotor, but embodying a iurther'modiiication of the invention.

As an example of one form in which the invention may beembodied, I showin the drawings the hubV assembly of a helicopter rotor attached to the upper end of a tubular shaft 5. In pian form the hub 6 is star-shaped, with three arms 1, each terminating at its outer end in a bearing collar 8, and each having a laterally directed bearing boss 9j Each collar 8 is supported, through the medium of a needle bearing I9, on an intermediate portion of a rotor blade II, the shank end of which is supported through the medium of an anti-friction bearing l2, in the bearing boss` 9 of anadjacent arm 1. y

' '.Ihe shank portions I3 of the three rotor blades I I are thus arranged so as to dene an equilateral triangle, and the axes I4 of the blades are tangent to a circumference of the rotor axis having a substantial radius. The blades II extend tangentially from the hub. Because of this tangential arrangement of the blades, centrifugal pull against the blades when they are rapidly rotating, acting radially, as indicated by the vector line I5 in Fig. 5, will have a circumferential component'which is indicatedat I6, and this component will partially balance the aerodynamic drag against the blades, indicated by the arrow I1.

The blades II are rotatable in the bearings IIJ and I2'in order that their angles of attack may be changed to properly control the operation of the helicopter. So as to adjust and hold the respective blades in their adjusted positions, there is vattached to each shank I3 a crank arm I8. Each crank arm IB has a collar I9 provided with internal splines meshing with splines 29 in the respective shanks I3. The shanks I3 are tapered *tov permit the collars I9 to be slipped over the ends thereof into engagement with the splines 2U. The taper has the additional purpose of streamlining the Shanks I3 down to minimum weight, while preserving the most efficient lever arm shape for maximum strength Where strength is needed.

The shanks I3 are situated at a suicient radial distance from the' axis' of rotationso thatthe crank arms I 8 may have adequate length and yet terminate within the tubular shaft 5. The crank arms are extended into the shaft 5 through vertical slots 2I in the shaft 5 and in the central collar portion 22 of the hub I, by means of which the hub is attached to the shaft 5. Each crank arm I8 is connected at its inner end to a control rod 23 by means of a yoke 24 attached to the upper end of the rod, a bearing 25`mounted in an aperture in the end of the crank arm I8, and a pintle bolt 26 extending through the yoke 24 and through the bearing 25.

The crank arms I8 are offset from the rotor axis. This makes it possible to extend the arms I8 beyond the rotor axis so as to achieve maximum length in proportion to the distance between--the -blade axisV and the rotor axis, and so as to permit the control rods 24 to be properly spaced from each other within the shaft 5.

The hub spider 6 has top and bottom anges 21 and 28Y respectively, the central sleeve 22,` and Web portions 29 connecting the ang'es 21 and 28.

In the arm 1 the cross-sectional shape is' substantially that of an I-beam as shown in Fig. 3. The bosses 9 are formed in the web portion 29.v 'Collars 9 are formed as extensions ofthe flanges 21 and28.

At the end of each shank I3 is a ferrule 30 which has an internal buttress.V typethread 3| into which the reduced threaded end 32 of the shank I3 is threaded. The ferrule 39 is provided with an annular radially outwardly extending shoulder 33, which abuts a thrust bearing 34. The end thrust developed in the rotor blades by centrifugal force is transmitted from theshoulder tions 40 in order to secure the bracket 35 to the arm 1. V w Y Each bearing I2 takes a down load from the end of its associated blade shank I3, while the adjacent bearing I9 takes anuupload from the intermediate region Yoi the adjacent shank I3. The down load on the bearing `I2 partially balances the up load on the bearingnlil, and, as,V a result, the bending momenthupon the arm of the hub spider is considerably reduced, below that whichwould be appliedtog.l hub spider by rotor blades disposed radially.l lThis makes "it possible to employ a lighterhb spidertha 'would be required in a radial blade-arrangement The balancing Vof theupload on` the bearing 8 against the download on the'vbea'ring I2 is through the portion of the arm 1 connecting'thes'e bearings, and in order that the bending moment on this portion may be reduced to a minimum, the two bearings are located as closely together as is practicable. L g l.

The triangular arrangement of blade Shanks makes it possible to extend each blade shank con`A siderably past the rotor axis, and, consequently,= to locate the outer bearing I0 considerably closer tothe rotor axis than would benecessary in a radial blade arrangement, to obtain the same distancebetween outer and inner bearings.' AThus the invention provides for a spider'having arms of minimum length, otherfactorsjbeing equal;A

and thus contribtcs'to' the reduction'inweight, I

provides a more compact and sturdy arrangement, and reduces aerodynamic drag.

With reference to Figs. 2, 3, and 4, it should be noted. that the anges 2l and 28 are fitted around the shanks I3 in such a manner that the assembled hub is substantially streamlined in the various circumferential cross sections through the arms l.

The invention provides an open hub construction which improves the accessibility to the parts thereof. Reference is here made to the structural or load bearing portions of the hub for the purpose of reducing aerodynamic drag. How'- ever, it will be desirable to cover this open hub structure with a light sheet metal cover of streamlined cross section, which may be easily attached to or detached from the basic hub structure.

The bearings 8 and 34 may be combined in a single bearing as shown in Fig. 6. In this modification of the invention, the blades IIa are hollow and have hollow shanks I3a which are provided with spherical bearing portions 8a, and are cut away as at 5I to receive the arms 'Ia of the hub spider. their ends with spherical bearing portions I2a which are socketed in the bearing portions 8a. The blade Shanks I3a are provided at their ends with spherical bearing portions 32a, which are socketed in the bearing portions I2a. This universal bearing connection between the spider la, the intermediate portion of one blade shank I3a and the end portion of another blade shank I3a permits the relative rotation of both blade Shanks with reference to the spider la.

In Fig. 7 I have shown another modification of the invention, in which each bearing I2b is located directly below its associated bearing 8b. This arrangement may be employed where a coning angle is given to the rotor blades. The arms 'Ib of the hub spider 6b are modified to accommodate this modified arrangement of the bearings.

In Fig. 8 I have shown another modification of the invention, applied to a single bladed rotor, in which the hub spider 6c has arms Ic and 'Id provided respectively with bearings I2c and 8c in which the shank I3 of the blade II is mounted. The control arm I8 may, in this instance, be arranged to intersect the axis of the rotor shaft 5. The offset arrangement of the blades is particularly advantageous in a single bladed rotor, as it adds stability to the operation of such a rotor.

I claim as my invention: j

1. In a rotor for rotor sustained aircraft including a plurality of blades having shanks that are spaced radially from the rotor axis and arranged to collectively define the perimeter of a polygon the center of which lies at the rotor axis with the blades extending tangentially therefrom; a hub and spider including a plurality of radiating arms each having a pair of coaxial adjacent bearings one of which is an end thrust bearing taking the centrifugal load of a respective blade at the end of the shank thereof and the other of which constitutes a journal support for said shank end, and each arm having a third bearing, aligned with the coaxial adjacent bearings of another arm, with the shank of another blade journalled therein each arm including integral means securely connecting said bearings together for directly balancing the thrust on said end thrust bearing against the load on said third bearing.

The arms Ia are provided at 2. In a rotor for rotor sustained aircraft in-` cluding a plurality of blades having shanks that are spaced radially from the rotor axis and arranged to collectively define the perimeter of a polygon the center of which lies at the rotor axis with the blades extending tangentially therefrom, each shank being provided at its end with a trunnion and, adjacent said trunnion, with a shoulder facing toward the blade tip; a hub and spider including a plurality of radiating arms each having an end bearing in which the end trunnion of a respective blade is journalled, and each having a second bearing aligned with the end bearing of another arm, in which the shank of another` blade is journalled, and a third bearing detachably attached to each arm, adjacent to and coaxial with the end bearing thereof, positioned intermediate said adjacent end bearing and the aligned second bearing, and arranged to take the centrifugal end thrust of the corresponding blade each arm including integral means securely connecting said bearings together for directly balancing the thrust on said end thrust bearing against the load on said third bearing.

3. In a rotor for rotor sustained aircraft including a plurality of blades having Shanks that are spaced radially from the rotor axis and arranged to collectively denne the perimeter of a polygon the center of which lies at the rotor axis with the blades extending tangentially therefrom; each shank being provided at its end with a trunnion and, adjacent said trunnion, with a shoulder facing toward the blade tip; a hub and spider including a plurality of radiating arms each having an end bearing in which the end trunnion of a respective blade is journalled and each having a second bearing, aligned with the end bearing of another arm, in which the shank of another blade is journalled; a bracket detachably secured to each arm intermediate the end thrust bearing thereof and the aligned second bearing of another arm, said bracket having an opening through which the shank of a respective blade extends, and an end thrust bearing engaged between said bracket and the shoulder of the shank that extends through said bracket each arm including integral means securely connecting its bearings together for directly balancing the thrust on said end thrust bearing against the load on said second bearing. k

4. In a rotor for rotor sustained aircraft including a plurality of blades having shanks that are spaced radially from the rotor axis and arranged to collectively define the perimeter of a polygon the center of which lies at the rotor axis with the blades extending tangentially therefrom, each shank being provided at its end with a trunnion and, adjacent said trunnion, with a shoulder facing toward the blade tip, a hub and spider including a plurality of radiating arms each having an end bearing in which the end trunnion of a respective blade is journalled, each having a second bearing aligned with the end bearing of another arm and through which extends the shank which is journalled in the end bearing of the last mentioned arm; a bracket detachably secured to each arm adjacent and parallel to the end bearing thereof, and having an opening coaxial with said end bearing, through which the respective shank extends; an end thrust bearing mounted upon each blade shank and engaged against the shoulder thereof, and a self-aligning thrust connection between each end thrust bearing and the adjacent bracket each arm including integral means securely connecting its bearings together for directly balancing the thrust on'said end thrust bearing against theload-on said second bearing. W e 5. -Ina rotor-forVrotor-sustained aircraft including a plurality of blades having shanks that are spaced radially from the rotor axis and arranged to collectively define the perimeter of la polygon the center of which lies at the-rotor axis with the blades extending tangentially therefrom, each shank being provided at its end with a trun-l nion and, adjacent said trunnion, withv a shoulder facing towardthe blade tip; a hub and spider including a plurality of radiating arms each .having an end bearing in which the end trunnion of a respective lblade is journalled, and each arm having a second bearing aligned with the end bearing of another arm and through which extends the shank lthatv is journalled` in the last mentioned end bearing; each arm 4including a pair of spaced flanges embracing the end bearing thereof; an end thrust bracket embraced between the flanges of each arm and detachably secured thereto, said end thrust bracket being disposed in adjacent spaced relation to the end thrust bearing of its respective arm and havingan opening through which is extended the shank that is journalled in the last mentioned end bearing; and a thrust bearing carried upon said last mentioned shank and interposed between said bracket and the adjacent end bearing. p

6. In a rotor for rotor sustained aircraft including a plurality of blades having shanks that are spaced radially from the rotor axis and arranged to collectively dene the perimeter of .a polygon the center of which lies at the rotoraxis with the blades extending tangentially therefrom, each shank being provided at its end with a removable ferrule having an end trunnion and, adjacent to said trunnion, a flange; a hub and spider includinga plurality of radiating arms each having a pair of spaced anges and a Web portion between said flanges; an end bearing mounted in the web portion of each arm, the trunnion of a respective blade shank being journalled therein; a second bearing carried by each arm and aligned with the end bearing of another arm, said second bearing having journalled therein the shank that is journalled in the aligned end bearing; an end bracket embraced between the flanges of each arm, securing elements extended through said ange's and through the ends of said bracket, said bracket havmg a portion disposed in spaced parallel and adjacent relationship to a respective end bearing and having an opening Vthrough which a. respective shank .extends; and anendthru'stbearing interposedbetween said .bracket and the shoulder ofthe respective blade shank. A

7. A rotor as dened in claim 5, including a sleevein which said .trunnion and shoulderare integrally formed said sleeve having internal threads and said shank having a threaded end portion threaded into said sleeve.

, 8. In a rotor for rotor sustained aircraft, includinga pluralityof blades having Shanks that are spaced radially from the rotor axis and arranged to collectively denne the perimeter of a polygon the center of which lies at the rotor axis withV the blades extending tangentially therefrom; a hub and spider including a plurality of radiating arms each having an end ,thrust bearing taking the centrifugal load of a respective blade at the end ofY a shank thereofl and each having a second bearing in which the shank of another blade is journalled, said end thrust bearing and Second bearing being closely adjacent eachother and each arm including integral means securely connecting its bearings together for directly balancing the thrust on said end thrust bearing against the load on said second bearing, each of said arms including a vertical web portion and horizontal flanges projecting radially outwardly from'said web portion, said web portion and anges defining a channel in which a respective shank is partially received, a supporting ring for said second bearing, with which the outer end extremities of's'aid web and flange merge, and a. supporting ring for said end thrust bearing, formed in said web portion intermediate said end thrust bearing and said hub.

9. A rotor as defined in claim 8, wherein the flanges of adjacent arms are joined together to form continuous arcuate bracing means interconnecting the respective arms.

Y PIETER J. BROUWER.

REFERENCES CITED The following references are of record in the leof this patent:

UNITED STATES PATENTS Number Name Date 2,037,251 Mansson Apr. 14, 1936 2,080,522 Wilford May 18, 1937 2,352,342 Pitcairn June 27, 1944 2,352,404 Pitcairn June 27, 1944 

